DESCRIPTION: Fatty acid binding proteins (FABP) are a family of small cytosolic proteins that are abundant in a variety of tissues and in many organisms. It is likely that FABPs play important roles in the transport and metabolism of fatty acids. In this event alterations in these proteins might be involved in diseases in which fat metabolism is implicated and indeed recent evidence suggests that modification of the intestinal FABP may be linked to diabetes. Because there is considerable amino acid sequence variation in FABPs from different tissues it has generally been thought that the biochemical properties of these proteins would be tissue specific, yet until recently no evidence existed for such variability. During the past three years, however, our studies have demonstrated that the thermodynamic and kinetic properties of FA-FABP interactions are extremely sensitive both to the tissue origin of the FABP and to the molecular species of FA. The long-term goals of the present studies are (1) to provide a rigorous biochemical basis for understanding the physiologic role of these proteins, (2) to understand the molecular interactions that give rise to the observed tissue-specific heterogeneity of binding, and (3) to develop a variety of fluorescent probes of free fatty acids (FFA) that will have application in clinical medicine as well as biochemistry. Because FABPs can be grouped according to their sequence homologies and our initial studies of three of these groups reveal that thermodynamic features of FA binding are characteristic of these groups, he will first extend these kinds of studies to members of other groups. For each one of these groups we will then use site directed mutagenesis to alter amino acid residues that interact in the binding cavity and determine the interaction energies corresponding to each residue change. Finally, he will use the results of these studies to construct new FFA probes with novel binding and fluorescent spectroscopic properties.